Lymphocyte subpopulations in healthy newborn infants: comparison of cord blood values with values five days after birth.

Significant differences (p < 0.0001) were demonstrated in lymphocyte subpopulations both in cord blood and in venous blood samples obtained at day 5 from the same healthy infants. Numbers of T lymphocytes increased, especially CD4+/CD45RA+ cells, whereas numbers of B lymphocytes and natural killer cells decreased without changes in CD8+ and other cytotoxic cells.